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15
CHAPTER 3: Configuration
3.1.4 C
ONFIGURATION
S
WITCH
“S3”
Use the individual positions on DIP switch S3 to set antistream control,
receive (input) impedance, and point-to-point/multipoint, as well as to
enable or disable local and remote loopbacks. The factory-default settings are
summarized in Table 3-3 below.
Table 3-3. Switch S3 Summary
S3-1 and S3-2: Input Impedance
Set positions 1 and 2 of switch S3 to determine the Multi-Function LD Card’s
input impedance.
Choose the optimum impedance setting for your application. In long-
distance applications, the impedance of the cable must match the impedance
of the load (or resistor) of the Multi-Function LD Card: Thicker-gauge cables
require a lower ohm setting, while thinner-gauge cables require a higher ohm
setting. Also, higher data rates call for a lower ohm setting, and lower data
rates dictate a higher ohm setting. Table 3-4 below lists our recommendations
for setting this switch.
S3-1
S3-2 Input Impedance
On On 130 ohms
On Off 200 ohms (default)
Off On 320 ohms
Off Off High (minimum 2000 ohms)
Position Function Default Setting
S2-1 Input Impedance On
200 ohms
S2-2 Input Impedance Off
S2-3 Reserved N/A
S2-4 Pt.-to-Pt./Multipoint On Point-to-Point
S2-5 DTE Local Loopback Off Disabled
S2-6 DTE Remote Loopback Off Disabled
S2-7 Antistream Control Off
Disabled
S2-8 Antistream Control Off